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The average IQ is 100. What percentage of people have IQs between 80 and 120. (IQ is normally distributed with mean 100, SD=15)

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The average IQ is 100. What percentage of people have IQs between 80 and 120. (IQ is normally distributed with mean 100, SD=15)

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Compute Z and use the standard normal distribution table. Please see attached.

First compute Z corresponding to the IQ 80 and 120 from Z=(IQ-mean)/sigma.

Then, Z at 80 = (80-100)/15 = ...

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